This is a prospective longitudinal study of the association between Attention-Deficit/Hyperactivity Disorder (ADHD) and alcohol abuse. In this study, children with ADHD (n = 350+) were ascertained in their elementary school-aged years following their participation in the ADHD Summer Treatment Program at Western Psychiatric Institute and Clinic, University of Pittsburgh. This is by far the largest sample of its kind to examine the ADHD-alcoholism association. The non-ADHD group (n = 240 demographically similar subjects) was recruited during the first follow-up of the probands, when probands and controls ranged in age from 11 to 25 years old. In this cohort-sequential design, subjects are assessed annually through the developmental periods in which alcohol consumption is initiated, reaches its peak, and subsequently decreases in the general population. In the first five years of support, the sample was ascertained, the battery developed, and participants completed two waves of assessments. The third wave is currently underway. Preliminary findings from Wave 1 document that (1) ADHD is a risk factor for early starting, heavy consumption of, and problems with alcohol, (controlling for childhood conduct problems); (2) ADHD-control differences in alcohol problems are influenced by expectancies and the peer network; (3) family history of alcohol problems is greater in probands; and (4) treatment with stimulant medication is related to greater alcohol and other substance use. We propose to continue these annual assessments as the sample matures through young adulthood to extend our cross-sectional findings to the longitudinal, allowing testing of hypotheses regarding individual differences in the course, causes, and consequences of alcohol consumption within the ADHD sample and between the ADHD and non-ADHD samples (i.e., what differences between the groups explain alcohol vulnerability in the ADHD group). Unique features of the study include (1) the wealth of standardized and objective childhood data that characterize the proband sample in childhood, (2) complete information regarding lifetime stimulant treatment and school functioning, (3) a large sample size that will allow previously underpowered examinations of comorbidity; (4) assessment of nonalcoholic substances, and (5) comprehensive assessment of domains uniquely relevant to the development of alcoholism (e.g., alcohol expectancies, motives, peer substance use and attitudes, parental drinking, and family history of alcoholism).